Composition of Extrafloral Nectar Influences Interactions between the Myrmecophyte Humboldtia brunonis and its Ant Associates

Ant-plant interactions often are mediated by extrafloral nectar (EFN) composition that may influence plant visitation by ants. Over a 300 km range in the Indian Western Ghats, we investigated the correlation between the EFN composition of the myrmecophytic ant-plant Humboldtia brunonis (Fabaceae) and the number and species of ants visiting EFN. EFN composition varied among H. brunonis populations and between plant organs (floral bud vs. young leaf EFN). In general, EFN was rich in sugars with small quantities of amino acids, especially essential amino acids, and had moderate invertase activity. In experiments at the study sites with sugar and amino acid solutions and with leaf or floral bud EFN mimics, dominant EFN-feeding ants differentiated between solutions as well as between mimics. The castration parasite Crematogaster dohrni (northern study site) was the least selective and did not exhibit any clear feeding preferences, while the largely trophobiont-tending non-protective Myrmicaria brunnea (middle study site) preferred higher sucrose concentrations and certain essential/non-essential amino acid mixtures. The mutualistic Technomyrmex albipes (southern study site) preferred sucrose over glucose or fructose solutions and consumed the leaf EFN mimic to a greater extent than the floral bud EFN mimic. This young leaf EFN mimic had low sugar concentrations, the lowest viscosity and sugar: amino acid ratio, was rich in essential amino acids, and appeared ideally suited to the digestive physiology of T. albipes. This preference for young leaf EFN may explain the greater protection afforded to young leaves than to floral buds by T. albipes, and may also help to resolve ant-pollinator conflicts. The differential response of dominant ants to sugar, amino acids, or solution viscosity suggests that plants can fine-tune their interactions with local ants via EFN composition. Thus, EFN can mediate local partner-choice mechanisms in ant-plant interactions.

Distribution of coenzyme Q in rat liver cell fractions

COENZYME Q (CoQ), which is widely distributed in animal, plant and microbial sources, has been implicated in electron transport1 and generally assumed to be associated with mitochondria. However, it has also been found in non-mitochondrial fractions of green leaves, although it appears to be concentrated in mitochondria2. A similar distribution has now been demonstrated in rat liver cell fractions.

Divvying up an incubator: How parasitic and mutualistic fig wasps use space within their nursery microcosm

Differential occupancy of space can lead to species coexistence. The fig-fig wasp pollination system hosts species-specific pollinating and parasitic wasps that develop within galls in a nursery comprising a closed inflorescence, the syconium. This microcosm affords excellent opportunities for investigating spatial partitioning since it harbours a closed community in which all wasp species are dependent on securing safe sites inside the syconium for their developing offspring while differing in life history, egg deposition strategies and oviposition times relative to nursery development. We determined ontogenetic changes in oviposition sites available to the seven-member fig wasp community of Ficus racemosa comprising pollinators, gallers and parasitoids. We used species distribution models (SDMs) for the first time at a microcosm scale to predict patterns of spatial occurrence of nursery occupants. SDMs gave high true-positive and low false-positive site occupancy rates for most occupants indicating species specificity in oviposition sites. The nursery microcosm itself changed with syconium development and sequential egg-laying by different wasp species. The number of sites occupied by offspring of the different wasp species was negatively related to the risk of syconium abortion by the plant host following oviposition. Since unpollinated syconia are usually aborted, parasitic wasps ovipositing into nurseries at the same time as the pollinator targeted many sites, suggesting response to lower risk of syconium abortion owing to reduced risk of pollination failure compared to those species ovipositing before pollination. Wasp life history and oviposition time relative to nursery development contributed to the co-existence of nursery occupants.

Temporal associations in fig-wasp-ant interactions: diel and phenological patterns

In a complex multitrophic plant-animal interaction system in which there are direct and indirect interactions between species, comprehending the dynamics of these multiple partners is very important for an understanding of how the system is structured. We investigated the plant Ficus racemosa L. (Moraceae) and its community of obligatory mutualistic and parasitic fig wasps (Hymenoptera: Chalcidoidea) that develop within the fig inflorescence or syconium, as well as their interaction with opportunistic ants. We focused on temporal resource partitioning among members of the fig wasp community over the development cycle of the fig syconia during which wasp oviposition and development occur and we studied the activity rhythm of the ants associated with this community. We found that the seven members of the wasp community partitioned their oviposition across fig syconium development phenology and showed interspecific variation in activity across the day-night cycle. The wasps presented a distinct sequence in their arrival at fig syconia for oviposition, with the parasitoid wasps following the galling wasps. Although fig wasps are known to be largely diurnal, we documented night oviposition in several fig wasp species for the first time. Ant activity on the fig syconia was correlated with wasp activity and was dependent on whether the ants were predatory or trophobiont-tending species; only numbers of predatory ants increased during peak arrivals of the wasps.

Analysis of the amino acid sequences of plant Bowman-Birk inhibitors

Plant seeds contain a large number of protease inhibitors of animal, fungal, and bacterial origin. One of the well-studied families of these inhibitors is the Bowman-Birk family(BBI). The BBIs from dicotyledonous seeds are 8K, double-headed proteins. In contrast, the 8K inhibitors from monocotyledonous seeds are single headed. Monocots also have a 16K, double-headed inhibitor. We have determined the primary structure of a Bowman-Birk inhibitor from a dicot, horsegram, by sequential edman analysis of the intact protein and peptides derived from enzymatic and chemical cleavage. The 76-residue-long inhibitor is very similar to that ofMacrotyloma axillare. An analysis of this inhibitor along with 26 other Bowman-Birk inhibitor domains (MW 8K) available in the SWISSPROT databank revealed that the proteins from monocots and dicots belong to related but distinct families. Inhibitors from monocots show larger variation in sequence. Sequence comparison shows that a crucial disulphide which connects the amino and carboxy termini of the active site loop is lost in monocots. The loss of a reactive site in monocots seems to be correlated to this. However, it appears that this disulphide is not absolutely essential for retention of inhibitory function. Our analysis suggests that gene duplication leading to a 16K inhibitor in monocots has occurred, probably after the divergence of monocots and dicots, and also after the loss of second reactive site in monocots.

Context-dependency of a complex fruit-frugivore mutualism: temporal variation in crop size and neighborhood effects

The quantity of fruit consumed by dispersers is highly variable among individuals within plant populations. The outcome Of Such selection operated by firugivores has been examined mostly with respect to changing spatial contexts. The influence of varying temporal contexts on frugivore choice, and their possible demographic and evolutionary consequences is poorly understood. We examined if temporal variation in fruit availability across a hierarchy of nested temporal levels (interannual, intraseasonal, 120 h, 24 h) altered frugivore choice for a complex seed dispersal system in dry tropical forests of southern India. The interactions between Phyllanthus emblica and its primary disperser (ruminants) was mediated by another frugivore (a primate),which made large quantities of fruit available on the ground to ruminants. The direction and strength of crop size and neighborhood effects on this interaction varied with changing temporal contexts.Fruit availability was higher in the first of the two study years, and at the start of the season in both years. Fruit persistence on trees,determined by primate foraging, was influenced by crop size andconspecific neighborhood densities only in the high fruit availability year. Fruit removal by ruminants was influenced by crop size in both years and neighborhood densities only in the high availability year. In both years, these effects were stronger at the start of the season.Intraseasonal reduction in fruit availability diminished inequalities in fruit removal by ruminants and the influence of crop size and fruiting neighborhoods. All trees were not equally attractive to frugivores in a P. emblica population at all points of time. Temporal asymmetry in frugivore-mediated selection could reduce potential for co-evolution between firugivores and plants by diluting selective pressures. Inter-dependencies; formed between disparate animal consumers can add additional levels of complexity to plant-frugivore mutualistic networks and have potential reproductive consequences for specific individuals within populations.

Choosing an appropriate index to construct dominance hierarchies in animal societies: a comparison of three indices

A plethora of indices have been proposed and used to construct dominance hierarchies in a variety of vertebrate and invertebrate societies, although the rationale for choosing a particular index for a particular species is seldom explained. In this study, we analysed and compared three such indices, viz Clutton-Brock et al.'s index (CBI), originally developed for red deer, Cervus elaphus, David's score (DS) originally proposed by the statistician H. A. David and the frequency-based index of dominance (FDI) developed and routinely used by our group for the primitively eusocial wasps Ropalidia marginata and Ropalidia cyathiformis. Dominance ranks attributed by all three indices were strongly and positively correlated for both natural data sets from the wasp colonies and for artificial data sets generated for the purpose. However, the indices differed in their ability to yield unique (untied) ranks in the natural data sets. This appears to be caused by the presence of noninteracting individuals and reversals in the direction of dominance in some of the pairs in the natural data sets. This was confirmed by creating additional artificial data sets with noninteracting individuals and with reversals. Based on the criterion of yielding the largest proportion of unique ranks, we found that FDI is best suited for societies such as the wasps belonging to Ropalidia, DS is best suited for societies with reversals and CBI remains a suitable index for societies such as red deer in which multiple interactions are uncommon. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Male spacing behaviour and acoustic interactions in a field cricket: implications for female mate choice

Males of several acoustically communicating orthopteran species form spatially and temporally structured choruses. We investigated whether male field crickets of the species Plebeiogryllus guttiventris formed choruses in the field. Males formed spatial aggregations and showed fidelity to a calling site within a night, forming stable choruses. Within aggregations, the acoustic ranges of males overlapped considerably. We tested whether males within hearing range of each other interacted acoustically. The chirps of simultaneously calling males were aphasic with respect to each other and showed no significant alternation or synchrony of calls. Some individuals changed temporal features of their calling songs such as chirp durations and chirp rates in response to a simultaneously calling neighbour. The implications of these results for female mate choice are discussed

Genome-wide analysis and experimentation of plant serine/threonine/tyrosine-specific protein kinases

Protein tyrosine phosphorylation plays an important role in cell growth, development and oncogenesis. No classical protein tyrosine kinase has hitherto been cloned from plants. Does protein tyrosine kinase exist in plants? To address this, we have performed a genomic survey of protein tyrosine kinase motifs in plants using the delineated tyrosine phosphorylation motifs from the animal system. The Arabidopsis thaliana genome encodes 57 different protein kinases that have tyrosine kinase motifs. Animal non-receptor tyrosine kinases, SRC, ABL, LYN, FES, SEK, KIN and RAS have structural relationship with putative plant tyrosine kinases. In an extended analysis, animal receptor and non-receptor kinases, Raf and Ras kinases, mixed lineage kinases and plant serine/threonine/tyrosine (STY) protein kinases, form a well-supported group sharing a common origin within the superfamily of STY kinases. We report that plants lack bona fide tyrosine kinases, which raise an intriguing possibility that tyrosine phosphorylation is carried out by dual-specificity STY protein kinases in plants. The distribution pattern of STY protein kinase families on Arabidopsis chromosomes indicates that this gene family is partly a consequence of duplication and reshuffling of the Arabidopsis genome and of the generation of tandem repeats. Genome-wide analysis is supported by the functional expression and characterization of At2g24360 and phosphoproteomics of Arabidopsis. Evidence for tyrosine phosphorylated proteins is provided by alkaline hydrolysis, anti-phosphotyrosine immunoblotting, phosphoamino acid analysis and peptide mass fingerprinting. These results report the first comprehensive survey of genome-wide and tyrosine phosphoproteome analysis of plant STY protein kinases.

Crystal structure of hexanediamine-glutamic acid complex

Polyamines are some of the most important and ubiquitous small molecules that modulate several functions of plant, animal and bacterial cells. Despite the simplicity of their chemical structure, their specific interactions with other biomolecules cannot be explained solely on the basis of their electrostatic properties. To evolve a structural understanding on the specificity of these interactions it is necessary to determine the structure of complexes of polyamines with other, representative biomolecules. This paper reports the structure of the 1:2 complex of hexanediamine and L-glutamic acid. The complex crystallizes in the monoclonic space group P2(1) with a = 5.171(1) angstrom, b = 22.044(2) angstrom, c = 10.181(2) angstrom and beta = 104.51(1)-degrees. The structure was refined to an R factor of 6.6%. The structures of these complexes not only suggest the importance of hydrogen-bonding interactions of polyamines but also provide some insight into other complementary interactions probably important for the specificity of biomolecular interactions.

Plant aspartate transcarbamylase: An affinity chromatographic method for the purification of the enzyme from germinated seedlings

A simple and rapid affinity chromatographic method for the isolation of aspartate transcarbamylase from germinated seedlings of mung bean (Phaseolus aureus) was developed. A partially purified preparation of the enzyme was chromatographed on an affinity column containing aspartate linked to CNBr-activated Sepharose 4B. Aspartate transcarbamylase was specifically eluted from the column with 10 mImage aspartate or 0.5 Image KCl. The enzyme migrated as a single sharp band during disc electrophoresis at pH 8.6 on polyacrylamide gels. Electrophoresis of the sodium dodecyl sulfate-treated enzyme showed two distinct protein bands, suggesting that the mung bean aspartate transcarbamylase was made up of nonidentical subunits. Like the enzyme purified by conventional procedures, this enzyme preparation also exhibited positive homotropic interactions with carbamyl phosphate and negative heterotropic interactions with UMP. This method was extended to the purification of aspartate transcarbamylase from Lathyrus sativus, Eleucine coracona, and Trigonella foenum graecum.

Modification of the sugar specificity of a plant lectin: structural studies on a point mutant of Erythrina corallodendron lectin

A mutant of Erythrina corallodendron lectin was generated with the aim of enhancing its affinity for N-acetylgalactosamine. A tyrosine residue close to the binding site of the lectin was mutated to a glycine in order to facilitate stronger interactions between the acetamido group of the sugar and the lectin which were prevented by the side chain of the tyrosine in the wild-type lectin. The crystal structures of this Y106G mutant lectin in complex with galactose and N-acetylgalactosamine have been determined. A structural rationale has been provided for the differences in the relative binding affinities of the wild-type and mutant lectins towards the two sugars based on the structures. A hydrogen bond between the O6 atom of the sugars and the variable loop of the carbohydrate-binding site of the lectin is lost in the mutant complexes owing to a conformational change in the loop. This loss is compensated by an additional hydrogen bond that is formed between the acetamido group of the sugar and the mutant lectin in the complex with N-acetylgalactosamine, resulting in a higher affinity of the mutant lectin for N-acetylgalactosamine compared with that for galactose, in contrast to the almost equal affinity of the wild-type lectin for the two sugars. The structure of a complex of the mutant with a citrate ion bound at the carbohydrate-binding site that was obtained while attempting to crystallize the complexes with sugars is also presented.

Retention Time Variability as a Mechanism for Animal Mediated Long-Distance Dispersal

Long-distance dispersal (LDD) events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal) of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape) of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.

A meta-analysis of the traits affecting dispersal ability in butterflies: can wingspan be used as a proxy?

1. Dispersal ability of a species is a key ecological characteristic, affecting a range of processes from adaptation, community dynamics and genetic structure, to distribution and range size. It is determined by both intrinsic species traits and extrinsic landscape-related properties. 2. Using butterflies as a model system, the following questions were addressed: (i) given similar extrinsic factors, which intrinsic species trait(s) explain dispersal ability? (ii) can one of these traits be used as a proxy for dispersal ability? (iii) the effect of interactions between the traits, and phylogenetic relatedness, on dispersal ability. 3. Four data sets, using different measures of dispersal, were compiled from published literature. The first data set uses mean dispersal distances from capture-mark-recapture studies, and the other three use mobility indices. Data for six traits that can potentially affect dispersal ability were collected: wingspan, larval host plant specificity, adult habitat specificity, mate location strategy, voltinism and flight period duration. Each data set was subjected to both unifactorial, and multifactorial, phylogenetically controlled analyses. 4. Among the factors considered, wingspan was the most important determinant of dispersal ability, although the predictive powers of regression models were low. Voltinism and flight period duration also affect dispersal ability, especially in case of temperate species. Interactions between the factors did not affect dispersal ability, and phylogenetic relatedness was significant in one data set. 5. While using wingspan as the only proxy for dispersal ability maybe problematic, it is usually the only easily accessible species-specific trait for a large number of species. It can thus be a satisfactory proxy when carefully interpreted, especially for analyses involving many species from all across the world.

Structure, interactions and evolutionary implications of a domain-swapped lectin dimer from Mycobacterium smegmatis

Crystal structure determination of the lectin domain of MSMEG_3662 from Mycobacterium smegmatis and its complexes with mannose and methyl-alpha-mannose, the first effort of its kind on a mycobacterial lectin, reveals a structure very similar to beta-prism II fold lectins from plant sources, but with extensive unprecedented domain swapping in dimer formation. The two subunits in a dimer often show small differences in structure, but the two domains, not always related by 2-fold symmetry, have the same structure. Each domain carries three sugar-binding sites, similar to those in plant lectins, one on each Greek key motif. The occurrence of beta-prism II fold lectins in bacteria, with characteristics similar to those from plants, indicates that this family of lectins is of ancient origin and had evolved into a mature system before bacteria and plants diverged. In plants, the number of binding sites per domain varies between one and three, whereas the number is two in the recently reported lectin domains from Pseudomonas putida and Pseudomonas aeruginosa. An analysis of the sequences of the lectins and the lectin domains shows that the level of sequence similarity among the three Greek keys in each domain has a correlation with the number of binding sites in it. Furthermore, sequence conservation among the lectins from different species is the highest for that Greek key which carries a binding site in all of them. Thus, it would appear that carbohydrate binding influences the course of the evolution of the lectin.